Hi Mathijs,
You can in parts still use the Blender manual and tutorials. But i would suggest to use the Bforartists manual where possible. The features are of course the same. But we have quite a few things different in the UI. The node editors are still quite similar though. The only real difference is that we have the content of the add menu in the sidebar too for quicker access.
It is hard to tell what is failing for you without to know the details of what you do. But you talk about shader editor. The viewer node is a node from the compositor editor. And here i can just add and use it fine.
So could you please give me a few more details, like in what editor type you try to add the node?
Kind regards
Reiner
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